I've managed to track this down to the auto-archive/visibility macros. To do this I had to troll through a long chain of posts on the subject from 2010. I'm still resolving a few details. One that that would help in future cases would be if the documentation at http://www.boost.org/development/separate_compilation.html could be updated. Right now it uses the "old" macros and doesn't mention visibility at all. It needs to be refactored somewhat to describe both auto-linking and visibility in such a way that the concepts to get so confused that the read loses track. Robert Ramey -- View this message in context: http://boost.2283326.n4.nabble.com/questions-regarding-GCC-visibility-tp4673... Sent from the Boost - Dev mailing list archive at Nabble.com.